Compression molding is an example high-volume molding process that may be used to produce complex components from a single set of mold halves. In general, a mold consists of a cavity half and a core half. During the compression molding process the alignment of the cavity half and the core half are maintained as the halves are brought together. Prior to the mold being closed, or in other words, prior to the mold halves being completely mated and in contact with each other, material is placed or injected into a mold cavity formed by the mold halves. Inner contour surfaces of the mold halves within a cavity area form the mold cavity. The mold is then compressed or completely closed through applied force to spread the injected material and fill the mold cavity. Pressure is applied until the injected material is cured to form a component in the shape of the mold cavity.
A compression mold assembly typically consists of leader pins and/or guides and compression locks, which are used to align and maintain alignment of the mold halves. The guides provide a semi-tight or rough alignment of the mold halves. The compression locks provide a tight or fine alignment of the mold halves. During the compression molding process the cavity half tends to rub on the guides and the adjacent surfaces of the core half in the compression lock areas. Wear plates have been incorporated in the stated areas to prevent chafing or galling of the contact surfaces of the mold halves. Thus, as the mold closes, the wear plates on the core half rub on and against adjacent surfaces on the cavity half or vice versa. Although the wear plates prevent galling on the mold contact surfaces, they wear over time. The fitting between the mold halves or between the wear plates and the adjacent mold half can become loose in the lock areas. The loose fit results in inaccurate alignment of the mold halves, which causes the mold halves to shift relative to each other. This shift can cause damage to the mold halves or a change in the parting line gap between the mold halves, which in turn can result in scrap parts.
Typically, shims are added to the backside of the wear plates to compensate for the wear on the wear plates. To add the shims the mold is opened and the mold halves are separated. The opening and separation causes the loss of accurate alignment of the mold halves. In addition, it is difficult to determine when, where, and how many shims are needed. The stated determinations can be further hindered due to wear on the guides, and the ability of the guides to be deflected during the closing of the mold. A considerable amount of downtime can be extended in adjusting the position of the wear plates.
Thus, there exists a need for an improved compensation technique in maintaining the consistent alignment of mold halves during a high-volume molding process that minimizes downtime.